The influence of pore pressure in assessing hydrocarbon prospectivity: a review

Assessing the prospectivity of a basin or a play is a complex process that combines a multitude of geological, geomechanical and geophysical analyses with the aim to de-risk whether a particular basin/play should be explored further. However, it is possible to group the analyses under five simple terms: source, charge, reservoir, trap, and seal. In basic terms, if a basin/play can be demonstrated to have a source of hydrocarbons, a reservoir to accept the charge and a trap and seal to limit the migration of the hydrocarbons any further then the ‘opportunity’ has been shown to be prospective for hydrocarbon exploration, i.e. de-risking has occurred. Typical elements of this de-risking process would include assessing the presence and quality of the source rock or building a structural and stratigraphic model from seismic amplitude data. Other components would be modelling porosity for instance. However, the particular focus of this paper is that many of the other components that need to be understood and modelled as part of the assessment of prospectivity are related to the pressure regime within a basin/acreage block in which a prospect is located. The focus of this paper is, therefore, to highlight and review those aspects of hydrocarbon prospectivity that pertain to reservoir quality, migration, maturation, prospect identification and hydrocarbon retention that are demonstrably influenced by pore pressure (Figure 1). It is important to note that whilst understanding the reservoir forms a key focus within such studies of prospectivity, the pore pressure within the bounding shales (relative to the reservoir) is also important to understand aside from the implications for well planning.